Common degenerative spinal diseases, such as chronic degeneration of an intervertebral disc of the spine, may result in substantial pain and discomfort for a patient. Frequently, diseases of this type need to be treated through surgical intervention, which may include replacing the affected disc(s) and potentially fusing the associated vertebrae through the use of an implant or other like device. In particular applications, adjacent vertebral bodies may be fused via an implant, through screw arrangements, and/or by using bone graft material to secure the vertebrae in a fixed state. Exemplary indications for such devices include, but are not limited to, spinal stenosis, degenerative disc disease with a loss of disc height, disc herniation, spondylolisthesis, retrolisthesis, and disogenic back pain.
In replacing a diseased intervertebral disc(s) and effecting fusion, it may also be necessary to ensure that proper spacing is maintained between the vertebral bodies. Stated differently, once the implant or other like device is situated between adjacent vertebrae, the implant or device should adequately recreate the spacing previously maintained via the excised intervertebral disc (e.g., in its natural condition). Various expandable implants have been designed for this purpose. As such, it is possible for a surgeon to adjust the height of particular intervertebral implants to intra-operatively tailor the implant height to match the natural spacing between vertebrae, or any desired implant height. This may reduce the number of different implants needed to accommodate the varying anatomical confines of different patients.
Certain components of expandable implants, however, such as plates forming a part thereof, may be subject to torsional forces and/or compressive forces upon distraction or implantation. In some cases, the expansion mechanism of the implant may serve to keep the plates in alignment with one another to counteract these forces. In addition, rods or support bars have been used to inhibit the effect of torsional forces acting on the plates.
Although several versions of expandable intervertebral implants are known, the need for an improved expandable implant, which is expandable in situ and provides structures for keeping plates of the expandable implant in alignment with one another remains.